Cyclic GMP and cyclic AMP have been proposed to have opposing roles in regulating cellular proliferation through alterations of nuclear function. The objective of this study is to better characterize the regulatory roles of cyclic GMP and cyclic AMP in the phosphorylation of non-histone chromatin phosphoproteins. Specific nuclear protein kinases (present normally or following translocation) which are regulated by cyclic GMP or cyclic AMP will be identified, purified and characterized. Possible alterations in the regulatory properties of non-histone chromatin phosphoproteins will be examined following their phosphorylation by these two classes of kinases. This will give further information about the regulatory roles of cyclic GMP and cyclic AMP in nuclear function and the control of cellular proliferation.